Although renewable energy from natural resources such as sunlight, wind, rain, and tides are typically clean, plentiful and relatively cheap, its use has been limited due to an inherent problem that renewable energy is not always available on demand. Compressed air energy storage is a way to store energy generated during periods of low energy demand for use during periods of high energy demands. It has been proposed to store compressed air in a high pressure environment such as deep underwater to avoid the costs of high-pressure vessels for storing the compressed air.
A compressed air energy storage device in development stages is described in an article published on Apr. 28, 2010 on www.energystorageforum.com/tag/compressed-air/downloaded from the internet on Jan. 27, 2010. The article discloses a pumpkin-shaped, underwater, compressed-air-storage devices being trialed at the University of Nottingham. It is described that the compressed-air-storage devices, constructed from steel and polymer, are designed to be pumped full of high-pressure air during times of high winds and low demand, with the stored energy used to turn turbines to create electricity when needed on the grid. The article states that the compressed-air-storage devices being trialed at the University of Nottingham could prove key to overcoming one of the main obstacles to Europe's long-term ambitions for utility-scale renewable-energy production—that peak power-generating times from offshore wind farms rarely match peak demands for electricity onshore.
Japanese Patent Application No. JP54011517 published on Jan. 27, 1979, entitled “Marine pressurized water type energy storing method,” the contents of which is incorporated by reference, describes a rigid dome shaped air storage tank including a water valve and an air pipe for storing pressure energy in a pressurized water vessel placed in or on the bottom of the sea with compressed air pumped in from an air compressor set in the marine space.
Japanese Patent Application No. JP63239320 published on Oct. 5, 1988, entitled “Underwater Energy Storage Device,” the contents of which is incorporated by reference, describes a hollow rigid bottomless case placed on the bottom of the sea for storing pressurized air. During the nighttime or the like where the surplus power is produced, a compressor is operated to feed pressurized air into the hollow case through a connecting pipe, and then, by forcing the seawater through a water passage hole, the electrical energy is stored as an air-pressure energy in the case. During the daytime, a generator is operated by making use of the pressurized air stored in the case.
Japanese Patent Application No. JP2271032, published on Nov. 6, 1990, entitled “Compressed air storage device for underwater installation and submerging method thereof,” the contents of which is incorporated by reference, describes an underwater installation compressed air storage device including main compressed air storage tank of bottomless shell construction and an additional weight adding part in its lower part. It is described that the device is softly landed to the sea bottom by releasing compressed air from a work deck barge and special underwater concrete is placed in the additional weight adding part through a pipe. The storage device is connected to a compressor and a turbine on the ground with a pipe.
Japanese Patent Application No. JP4121424 published on Apr. 22, 1992, entitled “Air storage power generation method and air storage power generation plant,” the contents of which is incorporated by reference, describes an underwater compressed air storage tank that floats above the seabed and has an opening at the bottom through which water is introduced and expelled. Water surrounding the tanks cools the air so that the temperature is decreased, while the pressure is maintained constant. Under condition of power shortage, the cooled compressed air is feed to a boost compressor and afterwards supplied to a combustor as combustion air through an air pipeline.